1. Technical Field
This invention relates to apparatus for reproducing information from data-carrying disks having recorded areas of varying size and/or characteristics.
2. Related Art
Conventional Compact Disk (CD) players are well known. A CD disk, arranged in accordance with the so-called xe2x80x9cred bookxe2x80x9d standard, includes an area carrying playback data and a table of contents (TOC) area carrying index information for the recorded area. The TOC information indicates the various playback track start points and total playing time of the recorded area. In order to play back the CD, a conventional CD player first accesses the TOC area and reads the index information therefrom, before accessing and playing back from the recorded area.
CD-recordable (CD-R) writer/players are also well known. A CD-R disk may be recorded over once, and only once, although it may be recorded in stages. A partially-recorded CD-R disk is referred to herein as an unfinalized CD-R. A specific finalizing process is required in order to convert the CD-R disk into a finalized disk which may be played back in a conventional CD player. A CD-R disk, arranged in accordance with the so-called xe2x80x9corange bookxe2x80x9d standard, includes a recorded area corresponding to the playback area of the CD disk and referred to as a program area (PA), a TOC area which generally remains unwritten until the disk is finalized, and a program memory area (PMA) which contains index information even when the disk is unfinalized, which information is written in the TOC area when the disk is finalized. The PMA is located in an inner part of the disk, which is inside any recording area specified in the xe2x80x9cred bookxe2x80x9d standard, and therefore many conventional CD players cannot access this area. Furthermore, the PMA is located in an area of an unfinalized CD-R in which no data is recorded, other than the PMA. The CD-R includes a pre-groove which can be detected by a CD-R writer/player, but not a conventional CD player. The pre-groove includes ATIP (absolute time in pre-groove) information, whereby the location of the PMA may be detected by a CD-R writer/player. The ATIP consists of a frequency modulated wobble of the pre-groove. Because a conventional CD player cannot detect the pre-groove, the ATIP information cannot be accessed, and therefore the location of the PMA cannot be readily determined.
Since the index information, which is otherwise read from the PMA, is necessary for playback, unfinalized CD-R disks generally cannot be played back by conventional CD players.
A solution to this problem is to provide the conventional CD player with the necessary means to reach the PMA, to detect the pre-groove and to read the ATIP. However, such a solution is not cost-effective.
U.S. Pat. No. 5,351,226 to Mizumoto et al., entitled Method and apparatus for reproducing information from a recordable optical disc regardless of whether an index area is detected as being present on the disk and a method of generating index information during reproduction of the information on the disk, describes a CD player which is capable of playing back unfinalized CD-R disks. In this arrangement, the index information is built up before a disk is played back by scanning the recorded area of the CD-R. A radial scan of the recorded area is carried out to detect a high frequency signal, which ends when the end of the recorded area is reached. The apparatus then jumps into the end track of the recorded area, reads sub-code information therefrom, wherefrom the relative time within the end track is ascertained, and a further jump to the start of the end track is used to read out further sub-code information for the end track. Next, sub-code data is read out from the penultimate track, and each of the preceding tracks in turn, in order to build up the index information. In this way, the unfinalized CD-R can still be played back, even though there is no index information recorded in the TOC area of the disk, and even though the CD player is not able to access the PMA.
The process of building up index information by scanning the disk should preferably be relatively short, since it is undesirable for a user to have to wait long periods before an unfinalized CD-R can be played back.
On the other hand, the index information should desirably be accurate. For example, a high degree of accuracy in the determination of the total playing time of the recorded area is desired. The reason for this may not be immediately apparent, insofar as an unfinalized disk may be played back fully even if the total playing time is not known to within a great deal of accuracy (for example, xc2x15 seconds). However, the total playing time is important if the disk is to be copied. If, for example, it is known that a disk onto which the copying is to be performed has a total blank area equal to the total playing time, a user will expect that the information on the disk to be copied can be accommodated therein. However, if the total playing time is incorrect, a part of the information to be copied may be lost. Furthermore, the index information built up in the scanning method may be used to prepare the TOC on the recorded disk, in which case such information will also be incorrect, and further recording problems may also occur.
In U.S. Pat. No. 5,351,226, cited supra, it is estimated that the end of the recorded area is detected to within 20 data track crossings. This corresponds to approximately 2xc2xd to 6 seconds of playing time, depending on the radial location of the end of the recorded area (with a constant linear velocity (CLV) system the amount of playing time per track crossing increases as the recorded area increases in size towards the outer periphery of the disk). It would be desirable to detect the end of the recorded area with a greater degree of accuracy.
In accordance with one aspect of the invention there is provided apparatus for reproducing information from data-carrying disks having recorded areas of varying size, wherein said apparatus comprises scanning means arranged to:
scan a disk coarsely to detect the end of a recorded area approximately; and
scan the disk finely in the area of the detected approximate end, to detect the end of the recorded area with greater accuracy.
The apparatus of the invention is thus able to detect the end of a recorded area relatively quickly, and with a desired degree of accuracy.
In accordance with a further aspect of the invention there is provided apparatus for reproducing information from data-carrying disks having recorded areas of varying characteristics, wherein said apparatus comprises scanning means for reading out data from the recorded area of a disk in order to detect index information for the disk, said scanning means being arranged to:
jump across a disk with predetermined intervals, to read out data at said predetermined intervals to detect partial index information for the disk, to analyze said partial index information, to jump to an area in which missing index information is judged to exist as a result of said analysis, and to read out data in said jumped to area to detect said missing index information.
The apparatus of the invention is thus able to detect at least partial index information whilst a scanning algorithm including jumps at predetermined intervals is carried out, thereby reducing the amount of time in which all the desired index information may be built up. To complete the desired index information, only the missing index information is then required.
Preferably, the size of the recorded area is still to be detected whilst the scanning means jumps across the disk with the predetermined intervals. Accordingly, at least an approximate size of the recorded area may be determined by means of the jumping with predetermined intervals, at the same time as the partial index information is detected.